Aqueous one step type lubricanting agent for efficient cold forging

ABSTRACT

A new aqueous lubricant of one process type used for high efficient cold forging of metallic materials is disclosed. The aqueous lubricant produces less industrial waste than conventional process, requires simple processing steps and provides improved lubricative performance.  
     The aqueous lubricant of the invention is comprising (A) a water soluble inorganic salt, (B) wax and (C) a metal salt of a fatty acid, those are dissolved or dispersed in water, and the ratio of (B)/(A) is 0.60˜0.70 and the ratio of (C)/(A) is 0.1˜0.3. The water soluble inorganic salt may be a sulfates, silicates, borates, molybdates and tungstates. The wax may be a synthetic wax of which melting point is in a range of 70˜150° C. The metal salt of a fatty acid may be a product prepared by reacting of C12˜C26 saturated fatty acids with metal selected from zinc, calcium, barium, aluminum magnesium and lithium.

FIELD OF THE INVENTION

[0001] In recent years, important parts for transportation machineries are often manufactured by applying cold forging of more than 70% of reduction area at one stroke to a steel of having the tensile strength of more than 300 N/mm². This cold forging process is usually called as “high efficient cold forging”. The present invention is related to a process to form a lubricative coating layer having excellent performance as lubricant onto the surface of a metallic material to be subjected to the high efficient cold forging without any previous chemical treatment. The present invention is related also to an aqueous lubricant of one process type used for high efficient cold forging, which facilitates to simplify the conventional lubricant layer forming processes, that is, to minimize space area required for forming the lubricative coating layer and not to increase industrial waste products.

PRIOR ART

[0002] Generally, in cold forging of metallic material, such as steel and stainless steel, coating layer is formed onto the surface of a metallic material. The coating layer may prevent a direct contact of the metallic material with a forging tool, and may decrease a surface defects of burning and biting of the metallic material which may arise by direct contact with the forging tool.

[0003] There are two types of the coated layers to be formed onto the surface of a metallic material, one of which is the type that a lubricant is being adhered directly onto the surface of the metallic material and the other is the type that a lubricant is being used onto the chemical layer being formed previously over the surface of the metallic material.

[0004] The lubricative coating formed by being adhered directly onto the surface of a metallic material has less adhesive performance than the lubricative coating by being used lubricant on to the chemical layer formed previously over the surface of the metallic material, and therefore, the former type is generally used for the cold forging with less amount of deformation.

[0005] In case of the latter type, the chemical layer is firstly formed on the surface of a metallic material through a chemical process such as phosphate layer forming process and oxalate layer forming process, which generally form chemical layer suitable as a carrier of a lubricant, and the lubricant having high lubricative property is used on to the chemical layer. In this type, the formed film has a bilayer structure consisting of a chemical layer as a carrier and a lubricant layer, which has high resistant property against surface defects.

[0006] From this reason, this type has been widely employed in the field such as wire drawing, tube drawing and cold forging. Particularly, in the cold forging where severe deformation is required, a process firstly forming the chemical layer comprising phosphate or oxalate and then using a lubricant onto the chemical layer is popularly employed.

[0007] The lubricant applied onto the chemical layer may be divided into major two groups in terms of the usage. The first group includes a lubricant to be mechanically adhered onto the chemical layer and the second group includes a lubricant which reacts with the chemical layer.

[0008] The first group of lubricant includes one prepared by using mineral oil, vegetable oil or synthetic oil as base oil and containing an extreme pressure additive in the base oil and one prepared by dissolving a solid lubricant, such as graphite and molybdenum disulfide, together with a binder component into the water. These lubricants may have advantage of easy for controlling the solution since they can be used simply by means of spray coating and dipping coating, however, as they have just a low lubricative properties, they tend to be used for a case where less amount of deformation of metallic material is required.

[0009] On the other hand, in the second group of lubricant, a reactive soap such as sodium stearate is used for a cold forging where particularly high lubricative property is required. The reactive soap reacts with the chemical layer and provides a layer of high lubricative property.

[0010] However, since the reactive soap gives a chemical reaction, control of the composition of the solution, temperature control for the chemical reaction and renewal control of the deteriorated solution, etc. are very important during the process. Further, for example, in the reaction of the phosphate layer with reactive soap, insoluble matter are produced in the solution along with the formation of lubricative layer. These insoluble matter are called as sludge, which is troublesome since it is required to be regularly excluded from the solution.

[0011] Further, the waste water arising in the formation process of the phosphate layer is containing the phosphate compounds. Such waste water should be appropriately treated in order to remove its contained phosphate compounds. In most case, such waste water containing phosphate compounds is subjected to neutralization with slaked lime to precipitate the phosphate. The precipitated phosphate compounds is separated from water and is discarded as industrial waste together with the sludge described above.

[0012] Recently, it is a big issue to reduce waste products from the industries for global environmental protection, and industrial waste containing phosphate compounds has been considered as serious problem in view of environmental protection. And therefore, new processes which do not produce waste products are highly desired.

[0013] Further, in the conventional process that produces a phosphate layer and uses a reactive soap on the phosphate layer, simplification and improvement of the process is required, since it requires wide area for the processing plant, greater time and complex control of the process. For example, in the process of producing the phosphate layer, frequent analysis of the phosphating solution on its free acidity, total acidity and concentration of accelerator has to be carried out by means of titration and the like. Further, in the reactive soap application process, analysis of free acidity and concentration of its constituent are regularly and manually carried out.

[0014] In order to solve the problems as described above, JP52-20967A, wherein a lubricant composition containing water soluble polymer or its aqueous emulsion as the base component, a solid lubricant and a film-forming agent is disclosed. However, no composition which has the same effect as the conventional process of using a chemical layer and a reactive soap has been obtained.

[0015] In order to solve the problems described above, another prior art of “Aqueous lubricant used for cold working of metallic material” disclosed in JP10-8085A can be cited. This prior art relates to an aqueous lubricant used cold forging of metallic material in which (A) water soluble inorganic salt, (B) solid lubricant, (C) at least one oil selected from a group consisting of chemical oil, animal oil, vegetable oil and synthetic oil, (D) surface active agent and (E) water are well dispersed and emulsified homogenously.

[0016] This prior art is related to an aqueous non-reactive type lubricant, and is aiming at simplifying the conventional three processes of phosphate layer formation, water rinsing and reactive soap application. That is, in this process, the lubricant film is formed directly on the surface of the metallic material by contacting the metallic material with the aqueous lubricant of one process type by means of dipping or the like, without forming any chemical layer previously on the surface of the metallic material. This type of lubricant is generally called as lubricant of one process type.

[0017] However, the lubricant according to this prior art is too unstable to use in an industrial scale since it contains emulsified oil component, and it is not steady to show a high lubricative properties in high efficient cold forging.

[0018] As another prior art, an invention of “A lubricant composition used for cold working of metallic materials” shown in JP2000-63380A can be cited. This prior art is directed to a lubricant comprising (A) synthetic resin, (B) water soluble inorganic salt and water, wherein the ratio of (B)/(A) by weight in solid state is in a range from 0.25/1 to 9/1 and the synthetic resin is either dissolved or dispersed in the composition. However, this composition is also not steady to show a high lubricative properties in high efficient cold forging.

DISCLOSURE OF THE INVENTION

[0019] Therefore, it is an object of the present invention to solve the problems of the conventional art as described above and to provide a new aqueous lubricant of one process type used for high efficient cold forging, which is being suitable for manufacturing of an important parts of transportation machineries, which is being simplified the operation without requiring any previous chemical treatment to form a coating layer and is favorable for keeping of good global environment.

[0020] The invention of the present invention have been made by investigation for solving the problems described above and have found that a suitable aqueous lubricant of one process type is obtainable by combining an water soluble inorganic salt, wax and metal salt of a fatty acid in an aqueous solution at a specific combining rate.

[0021] The aqueous lubricant of the present invention requires only one step of applying the lubricant and does not require 3 steps consisting of chemical reaction for phosphate layer formation, water rinsing and application with a reactive soap. These 3 steps are required in the conventional process. Also, the aqueous lubricant of the invention is a simplified process and may decrease to produce industrial waste than the conventional processes.

[0022] namely, the present invention is an aqueous lubricant of one process type used for high efficient cold forging characterized in that the aqueous lubricant comprises (A) a water soluble inorganic salt, (B) wax and (C) a metal salt of a fatty acid, wherein these component are dissolved or dispersed in an aqueous solution and the ratio by weight in solid state of (B)/(A) is in a range of 0.60˜0.70 and the ratio by weight in solid state of (C)/(A) is in a range of 0.1˜0.3. And the lubricant of the present invention is suitable for manufacturing an important parts of transportation machineries.

[0023] The preferable water soluble inorganic salt may be selected from a group consisting of sulfate, silicate, borate, molybdate and tungstate, and the wax is preferably a synthetic wax being dispersed in water and having a melting point in a range of 70˜150° C. Further, the metal salt of a fatty acid is preferably a compound obtained by reacting saturated fatty acid of C12˜C26 with at least one metal selected from a group consisting of zinc, calcium, barium, aluminum magnesium and lithium.

BRIEF DESCRIPTION OF DRAWINGS

[0024]FIG. 1 is a view showing the dimensional accuracy in cold forging process 2 shown later in the embodiment.

MODES FOR CARRYING OUT THE INVENTION

[0025] Now, the present invention is explained further in detail. The water soluble inorganic salt (A) used in the aqueous lubricant of the present invention is contained in order to give hardness and strength to the lubricative coating layer formed on the surface of the metallic material. The water soluble inorganic salt having such performance is required to have a property to be homogeneously dissolved in the aqueous lubricant and to form a strong lubricative coating layer when drying. As the inorganic salt giving such property, it is preferable to use at least one selected from a group consisting of sulfate, silicate, borate, molybdate and tungstate.

[0026] As the examples for the water soluble inorganic salt described above, sodium sulfate, potassium sulfate, potassium silicate, sodium borate (sodium tetraborate), potassium borate (potassium tetraborate), ammonium borate (ammonium tetraborate), ammonium molybdate, sodium molybdate and sodium tungstate may be given. Any of these salts may be used either alone or in combination of 2 or more salts.

[0027] As the wax (B), it is preferable to use a synthetic wax, though there is no specific limitation in the structure and the type. The wax may melt by a heat generated during the plastic deformation in cold forging, thereby improving the lubricative property of the lubricative coating layer. From this reason, it is preferable having a melting point in a range of 70 to 150° C. and being stable in aqueous lubricant so as to perform the preferable lubrication at the initial stage of the cold forging.

[0028] The practical examples for the wax may include microcrystalline wax, polyethylene wax, polypropylene wax and the like. These waxes are preferably contained in a form of water dispersion or water emulsion to the aqueous lubricant. The (B)/(A), namely the ratio by weight in solid state of the wax (B) relative to the water soluble inorganic salt (A) is preferably in a range of 0.6˜0.7. In high efficient cold forging, which is a hard process, there is possibility that the lubricative performance of the lubricative coating layer may be insufficient when the ratio described above is less than 0.6, while the adhesive performance of the lubricative coating layer may be insufficient when said ratio is more than 0.7.

[0029] The metal salt of a fatty acid (C) used in the present invention is for providing lubricative performance, and as the metal salt of a fatty acid, though there is no specific limitation in the type, it is preferable to use a product obtained by reacting saturated fatty acids of C12˜C26 with at least one metal selected from a group consisting of zinc, calcium, barium, aluminum, magnesium and lithium.

[0030] However, it is more preferable to use any of calcium stearate, zinc stearate, barium stearate, magnesium stearate and lithium stearate. The metal salt of a fatty acid used in the present invention exists in an aqueous lubricant in dispersed from, and a known surface active agent may be used when required.

[0031] The (C)/(A), namely the ratio of the aqueous inorganic salt (A) and the metal salt of a fatty acid (C) is set at a rate ranging from 0.1 to 0.3 by weight as the solid state. Under a severe working condition like the high efficient cold forging, the knockout property of the processed parts may be insufficient when said ratio is less than 0.1. However, under a severe working condition like high efficient cold forging, the accuracy of dimension of the obtained cold forged parts could be insufficient when said ratio is more than 0.3.

[0032] When a surface active agent is required for dispersing the metal salt of fatty acid and the wax in the aqueous lubricant, any surface active agent of nonionic, anionic, amphoteric and cationic type may be used. The nonionic surface active agent includes, but not specifically limited to, polyoxyethylene alkyl ester, polyoxyalkylene (ethylene or propylene) alkyl phenyl ether, polyoxyethylene alkyl ester comprising polyethylene glycol (or ethylene oxide) and higher fatty acid (C12˜C18, for example), polyoxyethylene sorbitan alkyl ester comprising sorbitan, polyethylene glycol and higher fatty acid (C12˜C18, for example).

[0033] The anionic surface active agent includes, but not specifically limited to, fatty acid salts, sulfuric esters, sulfonates, phosphoric esters and dithiophosphoric esters. The amphoteric surface active agent includes, but not specifically limited to, carboxylates either in amino acid configuration or betaine configuration, sulfuric esters, sulfonates, phosphoric esters. The cationic surface active agent includes, but not specifically limited to, amine salts of fatty acids, quaternary ammonium salts and the like. Each of these surface active agent may be used either alone or in combination of two or more of them.

[0034] The aqueous lubricant of one process type of the present invention is used for high efficient cold forging for metallic materials where more than 70% of section area reduction rate are given at one stroke. The important parts for transportation machineries used for automobiles and motorcycles, such as power train and chassis may be produced preferably by applying the aqueous lubricant of the present invention. The shape of the cold forging products is not particularly limited to cylindrical shape and is also applicable foe processing of more complicated configuration, such as gears and gear shafts.

[0035] Regarding the process to apply the aqueous lubricant of the present invention to the metallic material, though it is not specifically limited to, dipping method can be employed. The aqueous lubricant may satisfactorily be applied when the surface of the metallic material is fully covered with the aqueous lubricant by any method. After the coating, it is required to dry the coated aqueous lubricate.

[0036] The preferred coating operation can be given as below.

[0037] 1) Shot blasting

[0038] 2) Rinsing with hot water(Removal of soiled matter such as iron powder and heating the metallic material): 70˜90° C., 1˜3 minutes

[0039] 3) Application of the aqueous lubricant: 50˜70° C., dipping for 1˜3 seconds

[0040] 4) Drying: By air blowing under ambient temperature, 1˜2 minutes

[0041] 5) Cold forging

[0042] The weight of the formed lubricative coating layer (the amount of the coating) onto the surface of the metallic material is an important factor since it greatly affects the processing performance, such as lubricative performance and resistance to burning and biting. The weight of the formed coating layer may be calculated based on the weight difference between before and after the formation of the coating layer and the coated area of the metallic material.

[0043] Weight of the lubricative coating layer=(Weight after the formation of the coating layer−Weight before the formation of the coating layer)/(Area of the metallic material)

[0044] The weight of the formed lubricative coating layer suitable for the following cold forging process, it is preferable to be in a range of 5˜15 g/cm².

[0045] When the weight of the formed coating layer is less than 5 g/cm², sufficient lubricative performance cannot be provided, and causing burning defects during the high efficient cold forging. Whereas, when the weight of the formed coating layer exceeds 15 g/cm²,exfoliated lubricant film(dregs) may tend to remain in the cold forging mold, and the dregs in the cold forging mold may adversely affect the dimension accuracy of the cold forged products by forming a partial underfill portion of the forged products. The concentration of the constituent of the aqueous lubricant can be controlled so as to adjust the weight of the formed lubricative coating layer to be in the range described above.

EMBODIMENT EXAMPLES AND COMPARATIVE EXAMPLES [I]

[0046] Now, the present invention is further explained with referring Embodiment Examples and Comparative Examples given in the following.

[0047] <Metallic Materials>

[0048] 60,000 pieces of steel bar for counter shaft: Diameter 50 mm, length 140 mm.

[0049] Grade of steel: JIS G 4105 SCM420.

[0050] Surface pretreatment: Shot blasted aiming at removing scales for 14 minutes by using shot balls of 0.5 mm diameter.

[0051] <Lubrication Process A: One Process Type>

[0052] 1) Washing with hot water of 80° C.: For removal of shot blast powder and preliminary heating

[0053] 2) Lubrication process: Dipping for 1 min. into a lubricant of 60° C.

[0054] 3) Drying Air blowing under room temperature for 1 min. Total time (Time for processing+Time for transportation) for lubrication process A: 2 minutes and 30 seconds Total plant area necessary for lubrication process A: 9 m²

[0055] <Lubrication Process B: Conventional Type (Phosphate Layer+Reactive Soap)>

[0056] 1) Degrease by alkali degreasing agent: (Trademark: Parclean 357, manufactured by Nippon Parkerizing Co., Ltd), being diluted to 3% aqueous solution, 80° C., 10 minutes

[0057] 2) Washing with water: tap water, room temperature, 5 minutes

[0058] 3) Washing with acid: 10% aqueous solution of hydrochloric acid, room temperature, 5 minutes

[0059] 4) Washing with water: tap water, room temperature, 5 minutes

[0060] 5) Washing with water: tap water, room temperature, 5 minutes

[0061] 6) Chemical treatment by dipping in the phosphate film forming solution: Trademark: Palbond L3675XBM (manufactured by Nippon Parkerizing Co., Ltd), being diluted to 1% aqueous solution, 80° C., 10 minutes

[0062] 7) Washing with water: tap water, room temperature, 5 minutes

[0063] 8) Washing with water: tap water, room temperature, 5 minutes

[0064] 9) Treatment with reactive soap (Trademark: Paloob 236H manufactured by Nippon Parkerizing Co., Ltd.), being diluted to 1% aqueous solution, 90° C., 10 minutes

[0065] 10) Washing with hot water: tap water, 80° C., 5 minutes

[0066] 11) Drying: Air blowing under room temperature, 10 minutes

[0067] Total time (Time for processing+Time for transportation) necessary for lubrication process B: 60 minutes

[0068] Total plant area necessary for lubrication B: 90 m²

[0069] <Cold Forging Process 1: Resistance to Burning>

[0070] Section area reduction rate by forward extrusion: 77%

[0071] Cold forging mold: ultrahard alloy, high speed steel (Heis)

[0072] Cold forging punch: high speed steel (Heis)

[0073] Cold forging speed: 0.078 m/sec

[0074] <Cold Forging Process 2: Dimensional Accuracy by Resistance to Under Fill>

[0075] A shaft specimen having a diameter of 27 mm produced in the forging process 1 was subjected to annealing and then cold forged by forward extrusion as shown in FIG. 1 and the diameter at A part of FIG. 1 was measured.

[0076] <Evaluation>

[0077] Resistance to burning in cold forging process 1: Surface defects on the cold forging tool and cold forged products were visually observed. If surface defects are observed, it is not acceptable.

[0078] Dimensional accuracy in cold forging process 2: The diameter of the A part (FIG. 1) was measured. If cold forging is in good accuracy, the diameter of the A part is 27 mm. If the diameter is less than 27 mm it is in a state so-called “non-accurate”, which is not acceptable. A diameter of 27 mm was expressed as “o mm”, and for example, a measured diameter of 26.5 mm is expressed as “−0.5 mm”.

[0079] Simplification of the lubrication process: Evaluation was made based on the number of treatment steps in lubrication process and the total plant area necessary for lubrication process. Less treatment step and less area are preferable.

[0080] Environmental protection: Amount of waste products (drainage, sludge, etc) generated in treatment of 6,000 pieces of specimen was measured. Less amount for the treatment is preferable.

Embodiment Example 1

[0081] A lubricant 1 as below was used, and coating was carried out according to lubrication process A (one process type). Lubricant 1:

[0082] Aqueous inorganic salt: Sodium tetraborate

[0083] Wax: Polyethylene wax(1% by weight of nonionic surface active agent was added for improving dispersion).

[0084] Metal salt of fatty acid: Calcium stearate

[0085] Solid component ratio: (B)/(A): 0.70

[0086] Solid component ratio (C)/(A): 0.1

[0087] Weight of formed coating layer, g/cm²: 15

Embodiment Example 2

[0088] A lubricant 2 as below was used, and coating was carried out according to lubrication process A (one process type). Lubricant 2:

[0089] Aqueous inorganic salt: Potassium tetraborate

[0090] Wax: Microcrystalline wax(1% by weight of nonionic surface active agent was added for improving dispersion).

[0091] Metal salt of fatty acid: Calcium stearate-Solid component ratio: (B)/(A): 0.6

[0092] Solid component ratio (C)/(A): 0.3

[0093] Weight of formed coating layer (g/cm²): 15

Embodiment Example 3

[0094] A lubricant 3 as below was used, and coating was carried out according to lubrication process A (one process type). Lubricant 3:

[0095] Aqueous inorganic salt: Sodium tetraborate

[0096] Wax: Polyethylene wax (1% by weight of nonionic surface active agent was added for improving dispersion).

[0097] Metal salt of fatty acid: Calcium stearate

[0098] Solid component ratio: (B)/(A): 0.6

[0099] Solid component ratio: (C)/(A): 0.2

[0100] Weight of formed coating layer (g/cm²) 10

Embodiment Example 4

[0101] A lubricant 4 as below was used, and coating was carried out according to lubrication process A (one process type). Lubricant 4:

[0102] Aqueous inorganic salt: Sodium tetraborate

[0103] Wax: Paraffin wax (1% by weight of nonionic surface active agent was added for improving dispersion).

[0104] Metal salt of fatty acid: zinc stearate

[0105] Solid component ratio (B)/(A): 0.7

[0106] Solid component ratio: (C)/(A) 0.2

[0107] Weight of formed coating layer (g/cm²): 12

Comparative Example 1

[0108] A lubricant 5 as below was used, and coating was carried out according to lubrication process A (one process type). Lubricant 5:

[0109] Aqueous inorganic salt: Sodium tetraborate

[0110] Wax: Paraffin wax (1% by weight of nonionic surface active agent was added for improving dispersion).

[0111] Metal salt of fatty acid: Calcium stearate

[0112] Solid component ratio: (B)/(A): 1.0 (Out of the scope of the present invention)

[0113] Solid component ratio (C)/(A): 0.2

[0114] Weight of coated film (g/cm²): 10

Comparative Example 2

[0115] A lubricant 6 as below was used, and coating was carried out according to lubrication process A (one process type). Lubricant 6:

[0116] Aueous inorganic salt: Sodium tetraborate

[0117] Wax: Polyethylene wax (1% by weight of nonionic surface active agent was added for improving dispersion).

[0118] Metal salt of fatty acid: Calcium stearate

[0119] Solid component ratio (B)/(A): 0.7

[0120] Solid component ratio: (C)/(A): 0.5 (Out of the scope of the present invention)

[0121] Weight of coated film (g/cm²): 5

Comparative Example 3

[0122] A lubricant 7 as below was used, and coating was carried out according to lubrication process A (one process type). Lubricant 7:

[0123] Aqueous inorganic salt: Potassium tetraborate

[0124] Wax: Polyethylene wax (1% by weight of nonionic surface active agent was added for improving dispersion).

[0125] Metal salt of fatty acid: Calcium stearate

[0126] Solid component ratio: (B)/(A): 0.80 (Out of the scope of the present invention)

[0127] Solid component ratio: (C)/(A): 0.4 (Out of the scope of the present invention)

[0128] Weight of coated film (g/cm²): 15

Comparative Example 4

[0129] Coating was carried out according to the lubrication process B (Phosphate layer+Reactive soap).

[0130] <Results>

[0131] The results of the above described tests are shown in Table 1. As shown in Table 1, Embodiment Examples 1 to 4, where the aqueous lubricant of one process type of the present invention was used for high efficient cold forging, can form a coating layer with excellent performance, and are less number of treatment steps and less plant area for coating process. And, it is also understandable that the aqueous lubricant of the present invention may not produce much industrial waste products, that is waste drainage and waste sludge. In Comparative Example 1, where the ratio of (B)/(A) is out of the scope of the present invention, and in Comparative Example 2, where the ratio of (C)/(A) is higher than the scope of the present invention, burning are observed and inferior process performance are shown. For the coating obtained in Comparative Example 3, where both (B)/(A) and (C)/(A) are slightly different from the scope of the present invention, the dimensional accuracy was insufficient. Further, in Comparative Example 4, where (phosphate layer+reactive soap) were applied as same as a conventional process, similar process performance with that obtainable in the present invention are shown, however, this Comparative example requires more treatment steps and requiring more plant area necessary for process, and furthermore, it produces greater amount of waste products. TABLE 1 Performance Simplification (Resistance to Number Total plant Enviroment burning)/(Dimen- of treat- area for Drainage Sludge sional accuracy) ment step process (m²) (t) (kg) Embodiment Good/0 mm 3 9 0 0 Example 1 Embodiment Good/0 mm 3 9 0 0 Example 2 Embodiment Good/0 mm 3 9 0 0 Example 3 Embodiment Good/0 mm 3 9 0 0 Example 4 Comparative No good/−*1 3 9 −*1 −*1 Example 1 Comparative No good/−*1 3 9 −*1 −*1 Example 2 Comparative Good/−0.5 mm 3 9 −*2 −*2 Example 3 Comparative Good/0 mm 11 90 570 100 Example 4

EMBODIMENT EXAMPLES AND COMPARATIVE EXAMPLES [II]

[0132] <Metallic Materials>Steel bar of JIS G 4105 SCM420, Diameter: 50 mm, Length: 140 mm

[0133] <Lubrication process>Same as Lubrication Process A (one process type) as in embodiment example and comparative example [I].

[0134] <Usual cold forging>Section area reduction rate: 51%, Cold forging mold: High Speed Steel, Cold forging punch: High Speed Steel.

[0135] <High efficient cold forging>Section area reduction rate 77% Cold forging mold: High Speed Steel, Cold forging punch High Speed Steel.

[0136] <Lubricant>

[0137] Using the (A), (B) and (C) as below, and aqueous lubricant of one process type was prepared by adjusting (B)/(A) and (C)/(A) as Table 2 and tested.

[0138] Water soluble inorganic salt (A): Sodium tetraborate

[0139] Wax (B): Polyethylene wax

[0140] Metal salt of fatty acid (C): Calcium stearate.

[0141] <Results>

[0142] As shown in Table 2, in the usual cold forging of which section area reduction rate is 51%o, good results are obtained in all of the lubricant, namely, good resistance to burning as well as good dimensional accuracy can be obtained even though the ratio of (B)/(A) is less than 0.60 or more than 0.70. On the other hand, in the high efficient cold forging of which section area reduction rate of 77% good lubricant performance can be obtained only when the ratio of (B)/(A) is in a narrow range of 0.60 to 0.70. Similarly, in usual cold forging, good results are obtained even though the ratio of (C)/(A) is less than 0.1 or more than 0.3. However, in the high efficient cold forging, good results can be obtained only when the ratio of (C)/(A) is in a narrow range of 0.1 to 0.3. TABLE 2 One process type lubricant Resistance Dimensional (B)/(A) (C)/(A) Cold forging to burning Accuracy 0.55 0.2 Usual cold forgin ◯ ◯ 0.55 0.2 High efficient Δ Δ cold forging 0.65 0.2 Usual cold forgin ◯ ◯ 0.65 0.2 High efficient ◯ ◯ cold forging 0.75 0.2 Usual cold forgin ◯ ◯ 0.75 0.2 High efficient Δ Δ cold forging 0.65 0.05 Usual cold forgin ◯ ◯ 0.65 0.05 High efficient Δ Δ cold forging 0.65 0.15 Usual cold forging ◯ ◯ 0.65 0.15 High efficient ◯ ◯ cold forging 0.65 0.35 Usual cold forgin ◯ ◯ 0.65 0.35 High efficient Δ Δ cold forging

ADVANTAGE OF THE INVENTION

[0143] As described above, the aqueous lubricant of the present invention enables to form a coating layer having high performance to the surface of metallic materials. And less number of treatment steps and less plant area necessary for coating process are required in the present invention. In addition, aqueous lubricant of the present invention produces less industrial waste and is preferable for global environmental protection.

[0144] Further, the process of the present invention enables to improve the process by saving the treatment time of coating, by increasing the efficiency of coating, by saving the energy and by saving the production cost. 

1. An aqueous lubricant of one process type used for high efficient cold forging characterized in that the aqueous lubricant comprises (A) a water soluble inorganic salt, (B) wax and (C) a metal salt of a fatty acid, wherein these components are dissolved or dispersed in an aqueous solution and the ratio by weight in solid state of (B)/(A) is in a range of 0.60˜0. 70 and of (C)/(A) is in a range of 0.1˜10.3.
 2. The aqueous lubricant of one process type used for high efficient cold forging according to claim 1, wherein the water soluble inorganic salt is at least one selected from a group consisting of sulfate, silicate, borate, molybdate and tungstate.
 3. The aqueous lubricant of one process type used for high efficient cold forging according to claim 1 or 2, wherein the wax is a synthetic wax being dispersed in water and having the melting point of 70˜150° C.
 4. The aqueous lubricant of one process type used for high efficient cold forging according to claim 1, 2 or 3, wherein the metal salt of a fatty acid is a compound obtained by reacting saturated fatty acid of C12˜C26 with at least one metal selected from a group consisting of zinc, calcium, barium, aluminum, magnesium and lithium. 